High frequency apparatus



Dec. ,3, 1940. s; RAMO HIGH FREQUENCY APPARATUS Filed Nov. 30, 1939 .d w wtt m J haw w n t m 3% N ni .w M SWH Briefly stated, the invention utilizes the comanode 20, by which it is collected.

6 result in excitation of the two signal-generating 23 and-24. In order to maintain the beam in go I 45 electron gun, f r p ins an electron b The electrode 26 is associ ted with. tuned .5

50 a concentrated beam. The cylinder may either sociated with a circuit which includes a con- 50 55 an accelerating electrode it which is spaced the members 25, 26 and'llprovided proper correr nte'ane aie io" UNITED S m-res; PATENT: OFFlCE a HIGH APPARATUS Simon Ramo, Schenectady, N. Y., assignor to Gen- Y grytjlilectric Company, a co ration of New Application November 30, rest, Sei'lalNo. 366,951 .5 Claims. (CL 250-36) The present invention relates to high frefrom the cathode andwhich may be biased to a. quency electronic apparatus and has for its obsuitable positive-potential, say, several hundred ject the provision of an improved signal-generatvolts. v v 'ing system for use at frequencies so high that, Afterthe electron beam issues from thecylin- 5 electron transit time considerations play a condrical electrode I6 it is caused successively to f v trolling part in the operation of the apparatus. traverse two ring-like electrodes l8 and l l which A'more'speciflc object of the invention condeflnebetween them a region of substantially sists in the provision of an improved system for fixed beam velocity. Upon passage through the generating frequency modulated signals. electrode IS, the beam is caused to impinge on bination of two independent signal-generating In the operation of the. device described above,

- systems coupled to a single electron stream by the electrodes I8 and I! may appropriately be which they are adapted to be excited. The sig- -maintained at a potential several thousand volts nals developed by the two systems are of difabove the cathode, while the anode '20 should ferent frequency, andeach system is of such be held at a somewhat lower potential. for efg; character as to be exc'ted only upon the at- -flcient collectionof the beam. These-potential 'tainment of a particular velocity of the electron relationships may be established by means of stream. Consequently, by varying the stream suitable voltage sources, which areconvention-l velocity between the values which respectively ally represented in the dra ing batteries 22 systems,-the output of the apparatus as a whole focus during its passage along the axis of the Y may be caused to vary from one frequency to anenvelope one may employ a series of magnetic. other at a controllable rate. The ultimate effocusing coils (not shown), or other knownfect, therefore, is to produce a frequency modufocusing means. o5 lated signal. The combination of elements so-far described 25 The features which I desire to protect herein comprises means for prbducing-auriidirectional are pointed out with particularity in the appendbeam of electrons. Outside the envelope there ed claims. The invention itself, together with is provided a high'frequency electrode'arrange- ,further objects and advantages thereof, may ment adapted to cooperate with the beam. best be understood by reference to the following The electrodes which make up thehigh fredescription taken in connection with the acquency system include a-series' of sequentially mp y drawil in which Figure 1 lliu v arranged tubular conductive members which trates diagrammatically a high frequency .appaconcentrically surround the envelope and which 'ratus embodying the invention, and Figure 2 is 'are respectively numbered 25 to 29,;inclusive, a. ap a ep on u u i p aini The tubular members which bearodd numbers the operation of, the apparatus or Figure 1, are conductively" connected and are held at al The appar tus shown comprises an electron common potential by connection to the'posib am tube having an elongated tubular envelope tive terminal of the battery 24. The members portion II and an enlarged electrode contain- 26 and 28, on, the other hand, constitute inde- 4 ins Portion L T nvel pe is preferably conpendent electrodes which are capable of varying it e Of a low-1 insulatin m teri l, such in potentiaiat a desired frequency. For reasons a 'sla a'q k which will be given hereinafter, the members 7 The t bu r en b po HHS p i just referred to are ofdifierent lengths, as will at one end with mean su as a known type f be apparent from ins ection of the drawing. j

The wmbimtlon Which-18 0'" 9 this P circuit and signal-transmitting means which ,are pose'comprises-a cathode l4, indicated in dottedrespectively represented by the combination of I outline, and a focusing cylinder is for focus-- a condenser 32 and an inductance I3 and by an ing the electrons emitted from the cathode into antenna 35. Similarly, the electrode 28 is as be connected directly tothe cathod as shown, denser 31, an inductance 38 and an antenna 18.:

or mai a ne few'volts p ive or negative It is known that high frequency oscillations with respect to it. In order to accelerate the may be developed by means of an electrode comelectrons to'a desired extent there is provided 1 bination such as that which is represented by relation exists between the length of the intermediate electrode (26) and the velocity of the electrons traversing it. In this connection, let it be assumed that a cyclically alternating po- 5 tentlal is impressed between the member 26 and the members 25 and 21. It is clear that as a result of the potential gradients thus developed, electrons traversing the gap between members 25 and 26 are variously effected in velocity del0 pending on the portion of the potential cycle at which they reach the gap. Consequently, the

section of the electron stream passing through the member 26 at any given instant contains at various points along its length electrons of relatively high and relatively low velocity. The action of the faster electrons in catching up with the slower ones causes bunchlng of the electrons and. produces charge density' variations in the portion of the electron stream issuing from the member 26. Becauseof this fact, conduction currents of cyclically varying character are induced fin the member, 26 at its leaving end, so that an oscillating circuit appropriately connected to the member may be maintained in the excited :5 condition. Referring more specifically to the arrangement of Fig. 1, self-sustained oscillations .of the circuit 32, 33 may be developed provided the electron transit time through the member 26 is such as to correspond approximately to a quarter-cycle of the resonant frequency of the circuit, or to certain multiples thereof, including the fifth and ninth multiples.

It is apparent that for a fixed length of the member 26 the condition referred to in the pre- V 35 ceding paragraph can be obtained only for the particular velocity of the beam which is adapted to provide the proper electron transit time through the member. Consequently, excitation ofthe circuit 32,, 33 may be accomplished only provided the potential of the electrode [8 is ad- .iusted to a critical value. If this value is 'materially departed from, oscillation of the circuit will cease.

Inasmuch as the length of the member 23 is shown as being materially different from the length of the member 26, it will be readily understood'that the beam velocity which is required to cause excitation of the circuit associated with the former is different from that required to excite the circuit associated with the latter. Consequently, by changing the beam velocity from time to time it is readily possible to cause one or the other of the oscillating circuits to be selectively excited, Moreover, initiation of oscillation in one circuit will obviously be attended by cessation of oscillation in the other circuit. In accordance with my present invention provision is made for varying the electron beam velocity between the value which is appropriate for excitation of the signal-generating system associated with the member 26- and that which is appropriate for excitation of the system associated with the member 26. In this connection; there is shown as one possible means of accomplishing the desired end, a manually operable switch or key 42 which is adapted to be shunted across. the battery 23 so as to eliminate the effect of this battery in establishing the potential of the beam-velocity-determining electrode l8. A

g high resistance 43, connected in series with the battery and the switch, prevents the current drawn-during closure of the switch from being excessive. In the intended condition of operation of the apparatus, the relationship of .the' batteries 23 and 24 is such that with the switch may be caused to vary sequently,

32 in its open position, the beam velocity is appropriate to produce excitation of the electrode .26 and its connected circuit, whereas for the closed condition of the switch, the circuit associated with the electrode 26 is exclusively ex- 5 cited.-

By alternately opening and closing the switch 42 the signal output of the apparatus as a whole between the frequency of oscillation of the circuit 32, 33 and the fre- 10 quency of oscillation of the circuit 31, 38. Conthe signal which is transmitted by the apparatus will be frequency modulated as indicated by the graphical representation of Figure 2. In this figure, the irregular line A 15 represents the transition of the apparatus from the condition in which it generates a signal of frequency f1, corresponding to oscillation of the circuit 32, 33, to a condition in which it gencrates a higher frequency f2, corresponding to 20 oscillation of the circuit 31, 36. This variation of frequency may be given intelligence-conveying significance by controlling the length of the time interval during which either signal frequency is generated. Thus, it is readily possible to-adapt 25 the invention to a dot-dash system of intelli-' gence-communicatlon, such as is utilized in conventional code signalling practice. Receiving devices by which a signal of the type specified may be detected and translated are well known. 30

While I have described my invention by reference to a. particular embodiment thereof it will be understood that numerous modifications may be made by those skilled in the art without departing from the. invention. I therefore 5 aim in the appended claims to cover all such. equivalent modifications as fall within the true spirit and scope of the foregoing disclosure.

What I claim as new and desire to secure by Letters Patent of the United States is: m

- 1. In electronic signal-generating apparatus for use at frequencies so high that electron transit time considerations play a controlling part in the operation of the apparatus, the combination which includes means for producing an electron stream of controllable velocity, 8. pair of oscillating systems coupled -to said stream, one of said systems being adapted to be excited by the stream to generate a signal of a first desired frequency upon the attainment of a first predetermined 50 velocity of the stream and the other of said systems being adapted to be excited to generate a signal of a different desired frequency upon the attainment of a second predetermined velocity of the stream, and means for repeatedly varying the 55 velocity of the stream between its first and second predetermined values, thereby to cause the signal output of the apparatus to vary between the said' two desired frequencies.

2. In electronic signaling apparatus for use at 6 frequencies so high that electron transit time considerations play a controlling part in the operation of the apparatus, the combination which includes means for producing a beam of electrons of controllable velocity, a series of con- 55.

ductive members successively coupled to the beam at spaced points along the beam path, the di-'- mensions of certain ofsaid members being such as to assure effective mutual reaction of the members and the beam for a'first attainable beam 70 velocity, and the dimension of certain others of said members being such as to assure effective mutual reaction of the members and the beam for a second attainable beam velocity, an oscillating system including said certain members for de- 75 Ire - path;

eration of the apparatus, the combination whichincludes means for producing a beam of electrons of controllable velocity, a series of variously dimensioned conductive tubular members surrounding the beam at sp'acedpoints' along its reaction of the members and the beam for a first attainable beam velocity, and the axial dimensions of certain others of said members being such as to assure eifective mutual reaction of suchmembers and the beam for a second attainable beam velocity, an oscillating system including said certain members, another oscillating system including said others of said members, and means for varying the beam. velocity between its said: first and second attainable values, thereby sucthe axial dimensions of certain of said members being such as to assure effective mutual cessively and independently to excite the oscillating systems.

4. In electronic signaling apparatus, for use at frequencies so high that electron transit time considerations play a controlling part in the operation of the apparatus, the combination which includes means for producing a beam of electrons of controllable velocity, means to control the velocity of said electrons topredetermined values,

a first oscillatory means excitable to oscillation at one said velocity coupled to said beam and a second oscillatory means excitable to oscillation at another said velocity likewise coupled to said beam.

5. In electronic signaling apparatus for use at frequencies so high that electron transit time considerations play a controlling part in the operation of the apparatus, the combination which includes means for producing a beam of electrons of controllablevelocity, means to control the velocity oi! said electrons to predetermined values,

means to derive oscillatory current of one irequency from said beam at one said velocityand other means to derive an oscillatory current or a second frequency from said beam at a second said velocity.

SIMON RAMO. 

